JP2014169395A - Oily ink composition for ballpoint pen and oily ballpoint pen using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oily ink composition for a ballpoint pen adding a thixotropic property with no generation of "plumping phenomenon" or "direct current phenomenon".SOLUTION: There is provided an oily ink composition for a ballpoint pen containing at least a coloring agent and an organic solvent, and further a polyurethane resin (A) represented by the general formula shown below, where n is 3 to 15, Rand Rare each an aliphatic hydrocarbon having 2 to 6 carbon atoms.

Description

  The present invention relates to an ink composition for oil-based ballpoint pens and an oil-based ballpoint pen.

  Two types of ink for ballpoint pens are conventionally used: organic solvents, colorants such as dyes and pigments, oil-based inks containing resins, and water-based inks containing water-based solvents, dyes and pigments. Exists. Recently, gel inks containing water-based solvents, dyes, pigments and other colorants, and gelling agents have been developed. Gel ink is a gel with a high viscosity inside the refill by adding a gelling agent to the water-based ink. When the ink is subjected to a shearing force by a ball during writing, the viscosity is lowered, which makes smooth writing. Provides the effect of obtaining a taste. In addition, on the paper surface, the ink returns to the original gel state and has an effect that the ink does not easily spread. In this way, the property that a highly viscous gel is fluidized with its viscosity lowered by shearing force and then gelled again is called thixotropic property. In recent years, attempts have been made to impart the above-described effects of gel ink to oil-based ballpoint pens.

  As a means for imparting thixotropic properties to ink, various organic compounds or inorganic compounds are used. Conventionally, metal soaps, hydrogenated castor oil, fatty acid amides, dibenzylidene sorbitol and the like have been used as organic compounds, and silica, bentonites and the like have been used as inorganic compounds.

  Japanese Patent Application Laid-Open No. 7-196972 describes fatty acid amide wax, hydrogenated castor oil and the like as viscosity adjusting agents capable of forming a network structure viscosity in oil-based ink.

  Japanese Patent Application Laid-Open No. 2003-226826 discloses adding a urethane compound having at least a urethane bond and an amide bond in the molecule in order to prevent the pigment in the ink from settling.

  However, even if the oil-based ink composition is added with these compounds, sufficient thixotropic properties may not be imparted if the combination with an organic solvent is not appropriate.

JP 7-196972 A JP 2003-226826 A

  The present invention imparts sufficient thixotropic properties, and in a state where the ink is excessively accumulated at the tip end portion of the chip during writing and is caused by the “bottom phenomenon” caused by the transfer to the paper surface, or in a state where the pen tip portion is directed downward. An ink composition for an oil-based ballpoint pen that does not generate a “direct current phenomenon” in which ink leaks is provided.

  In order to solve the above-mentioned problems, the present inventor has conducted intensive research. As a result, in the ink composition for oil-based ballpoint pens containing a colorant, an additive, and an organic solvent, the polyurethane resin (A) having a specific structure is used as an ink. The inventors have found that these problems can be solved by adding them in, and thus completed the present invention.

（上式中、ｎは３〜１５、Ｒ₁、Ｒ₂はそれぞれ炭素数２〜６の脂肪族炭化水素である）
を含むことを特徴とする油性ボールペン用インク組成物。 That is, the present invention
(1) An oil-based ballpoint pen ink composition comprising at least a colorant and an organic solvent, wherein the ink composition further comprises a polyurethane resin (A) represented by the following general formula:

(In the above formula, n is 3 to 15, R ₁ and R ₂ are each an aliphatic hydrocarbon having 2 to 6 carbon atoms)
An ink composition for oil-based ballpoint pens comprising:

(2) The ratio of the viscosity at a shear rate of 3.8 sec ^{−1 to} the viscosity at 25 ° C. and a shear rate of 38 sec ⁻¹ of the ink composition is 1.2 to 4, described in (1) An ink composition for oil-based ballpoint pens.

(3) The ink composition for oil-based ballpoint pens according to (1) or (2), wherein the viscosity of the ink composition at 25 ° C. and a shear rate of 380 sec ⁻¹ is 100 mPa · s to 1000 mPa · s. .

(4) The oil-based ballpoint pen according to any one of (1) to (3), wherein the amount of the polyurethane resin (A) added is 0.1 to 5% by mass with respect to the total mass of the ink composition. Ink composition.

(5) The ink composition for a pressurized oil ballpoint pen as described in (1) or (2), wherein the ink composition has a viscosity of 100 to 5000 mPa · s at 25 ° C. and a shear rate of 380 sec ⁻¹ .

(6) The addition amount of the polyurethane resin (A) is 0.1 to 10% by mass with respect to the total mass of the ink composition, (1), (2), or (5) An ink composition for pressurized oil ballpoint pens.

(7) A ballpoint pen equipped with the oil-based ballpoint pen ink composition according to any one of (1) to (6).

  The ink composition for oil-based ballpoint pens of the present invention has sufficient thixotropic properties. In addition, the ink composition for oil-based ballpoint pens of the present invention can suppress the occurrence of bloating and direct current phenomena.

  The oil-based ballpoint pen ink composition of the present invention contains a polyurethane resin (A) having the following structural formula as a thixotropic agent.

（上式中、ｎは３〜１５、Ｒ₁、Ｒ₂はそれぞれ炭素数２〜６の脂肪族炭化水素である）

(In the above formula, n is 3 to 15, R ₁ and R ₂ are each an aliphatic hydrocarbon having 2 to 6 carbon atoms)

  This polyurethane resin (A) gels the ink by forming a continuous network structure in the ink composition, and once flows at the time of shear breaking when the ink is applied with a shearing force by a ball at the time of writing, the network structure is again formed. To increase the apparent viscosity. When the ink for ballpoint pens is stored at a high temperature, it is necessary that the network structure be present stably without being destroyed.

  In the polyurethane resin (A) according to the present invention, n in the structural formula is preferably 3 to 15. When n is less than 3, sufficient thixotropic properties are not imparted, which is not preferable. On the other hand, when n is larger than 15, the solubility in organic solvents may be lowered, or the thixotropic property may become too strong, which is not preferable. The molecular weight (Mn) of the polyurethane resin (A) is preferably 1,000 to 4,000.

Specific polyurethane resins (A) are, for example, A1 to A3 having the following structural formula:

  The polyurethane resin (A) used in the ink composition of the present invention is synthesized by the reaction of hexamethylene diisocyanate and a diol. Two or more types of polyurethane resins (A) according to the present invention having different structures may be used as the thixotropic agent.

  The polyurethane resin (A) used in the present invention can be prepared by putting it into a flask equipped with a reflux condenser together with an organic solvent, stirring the mixture at 120 ° C. until it becomes uniform, and allowing to cool at room temperature.

  As described above, the polyurethane resin (A) according to the present invention can be used alone or in combination. In addition, the polyurethane resin (A) according to the present invention can be used in combination with other known thixotropic agents, for example, organic materials such as fatty acid amide wax and polyethylene oxide, and inorganic materials such as silica and bentonite.

  The amount of the polyurethane resin (A) of the present invention added to the ink composition is preferably 0.1% by mass or more based on the total mass of the ink composition. When the addition amount is less than 0.1% by mass, a sufficient network structure cannot be maintained in the ink, and the intended effect cannot be exhibited. There is no particular upper limit on the amount added, but if it is added in a large amount, the ink loses its fluidity and may cause problems in the performance of the oil-based ballpoint pen. For example, when used for a non-pressurized type oil-based ballpoint pen ink, the addition amount is preferably 5% by mass or less. When used for a pressurizing type oil-based ballpoint pen ink, the upper limit of the amount added is approximately 10% by mass or less. The type of ballpoint pen that pressurizes refers to a ballpoint pen that supplies ink to the pen tip by pressure rather than by its own weight, and ink is supplied more abundantly than a normal oil-based ballpoint pen. For this reason, writing performance is maintained even for ink with poor ink fluidity.

  Solvents that have been identified as organic solvents that gel with the polyurethane resin (A) include butanol, benzyl alcohol, and 3-methoxy-3-methyl-1-butanol as alcohols.

Further, ether solvents that are gelled together with the polyurethane resin (A) include ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene Glycol monobenzyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene Glycol monobutyl ether, tripropylene glycol monomethyl ether.
It has been found that, for example, glycol solvents, glycol acetate solvents, and ketone solvents other than the above do not gel when used together with the polyurethane resin (A).

As the colorant, various colorants that can be used in conventional inks such as dyes, pigments, or mixtures of dyes and pigments can be used.
Dyes that can be used in the present invention include commercially available dyes and organic solvent-soluble dyes classified as solvent dyes in the color index, for example. Specific examples of the solvent dye include Bali First Black 3806 (CI Solvent Black 29), 3807 (trimethylbenzylammonium salt of the dye of CI Solvent Black 29), Spirit Black SB (C.I. Solvent Black 5), Spiron Black GMH (CI Solvent Black 43), Bali First Red 1308 (a salt-form of a dye of CI Basic Red 1 and a dye of CI Acid Yellow 23), Bali First Yellow AUM (Salt Form of Dye of CI Basic Yellow 2 and Dye of CI Acid Yellow 42), Spiron Yellow C2GH (Organic Acid Salt of Dye of CI Basic Yellow 2) , Spiron Violet CRH (CI Solvent Violet 81) Bali First Violet 1701 (salt salt of dyes of CI Basic Violet 1 and CI Acid Yellow 42), Spiron Red CGH (organic acid salt of CI Basic Red 1 dye), Spiron Pink BH ( CI Solvent Red 82), Nigrosine Base EX (CI Solvent Black 7), Oil Blue 603 (CI Solvent Blue 5), Neozapon Blue 808 (CI Solvent Blue 70), etc. Is mentioned.

  Examples of pigments that can be used in the present invention include inorganic facials such as carbon black, graphite, and titanium dioxide pigments, constitutional facials such as talc, silica, alumina, mica, and alumina silicate, azo pigments, and condensed azo pigments. Organic pigments such as phthalocyanine pigments, anthraquinone pigments, quinacdolin pigments, isoindolinone pigments, diketopyrrolopyrrole pigments and various lake pigments, fluorescent pigments, pearl pigments, metallic pigments such as gold and silver. In addition, graphite (graphite) can be used as a black pigment and lubricant, artificial graphite and natural graphite can be used, and graphite of various scales and sizes can be used, such as graphite on scale, massive graphite, and earthy graphite. .

  As the colorant used in the present invention, the above-mentioned dyes and pigments can be used alone, or the above-mentioned dyes and pigments can be mixed and used. The amount of the colorant can be 1 to 60% by mass, preferably 5 to 50% by mass, based on the total amount of the ink composition of the present invention.

  Various resins may be used in the ink composition of the present invention. These resins are added for the purpose of improving the fixability of the ink, preventing the show-through of the handwriting, adjusting the viscosity as a dispersant such as a pigment, and promoting the dissolution of the dye. As the resin, any resin conventionally used for oil-based ballpoint pen inks can be used. For example, condensation resin of ketone and formaldehyde such as toluenesulfonamide / epoxy resin, cyclohexanone, acetophenone, urea, etc., condensation resin of cyclohexanone and resin hydrogenated to them, maleic acid resin, copolymer of styrene and maleic acid ester , A copolymer of styrene and acrylic acid or an ester thereof, polyvinyl pyrrolidone, polyvinyl butyral, polyvinyl acetal, polyamide that is a condensate of polymerized fatty acid and polyamines, epoxy resin, polyvinyl alkyl ether, coumarone-indene resin, polyterpene, Terpene resins, terpene-phenol resins, xylene resins, rosin resins and their hydrogenated products, rosin-modified maleic acid resins, vinyl pyrrolidone vinyl acetate copolymers, polymethacrylate Esters, polyacrylic acid polymethacrylic acid copolymer, polyoxyethylene and phenolic resins. These resins can be used alone or in combination. The amount of the resin varies depending on the purpose of use, but is generally 0 to 60% by mass, preferably 0 to 50% by mass, based on the total amount of the ink composition of the present invention.

  In addition to the components described above, various additives that can be compatible without adversely affecting the ink, for example, a dispersant, a rust inhibitor, an antifungal agent, and a surfactant, as needed, in the present invention. A lubricant, a wetting agent, and the like can be blended. The additive to be used can be variously changed according to the mode of the writing instrument using the ink composition of the present invention. For example, lubricants such as higher fatty acids, metal soaps, and phosphate esters, and nonionic surfactants having a long-chain alkyl group can be added.

The ink composition for oil-based ballpoint pens of the present invention can be suitably used as a so-called gel ink ballpoint pen ink composition that has less blur in drawn lines and realizes light writing. In this case, the ratio of the viscosity at the shear rate of 3.8 sec ^{−1 to} the viscosity at the shear rate of 38 sec ⁻¹ (3.8 sec ⁻¹ / 38 sec ⁻¹ ) of the ink composition at 25 ° C. is 1.2. It is preferably ~ 4. When the viscosity ratio is less than 1.2, a direct current phenomenon is likely to occur particularly when the viscosity is low, and the pigment may settle when a pigment or the like is added. If the viscosity ratio exceeds 4, it is not preferable because it tends to cause blurring or the ink following ability is deteriorated and adversely affects writing.

Further, the ink composition for oil-based ballpoint pens of the present invention is suitably used for oil-based ballpoint pens having a low viscosity and imparting a light and smooth writing feeling. The viscosity at 25 ° C. and a shear rate of 380 seconds ⁻¹ is 100 mPa · It is preferable that it is s-1000 mPa * s. The viscosity at a shear rate of 380 seconds ^-1 is a value close to the physical properties obtained when the ball rotates at the time of writing. When this viscosity is less than 100 mPa · s, the ink pen viscosity is low, and the ballpoint pen seat is damaged. Undesirable phenomena occur, such as giving, feeling tingling at the time of writing, or being unable to suppress ink bleeding. On the other hand, when the viscosity exceeds 1000 mPa · s, light writing feeling is lost, which is not preferable.

Moreover, when using the ink composition for oil-based ball-point pens of this invention for a pressurized ball-point pen, it is preferable that the viscosity in 25 degreeC and 380 second ^-1 is 100-5000 mPa * s. This is because the pressure ballpoint pen supplies abundantly ink to the pen tip, so that even when the ink viscosity is higher than that of a normal oil-based ballpoint pen, a light writing feeling is maintained, but the viscosity is 5000 mPa · s or more. Then, the writing feeling becomes heavy, which is not preferable.

  The ink refill filled with the oil ballpoint ink composition of the present invention may be filled with an ink follower at the rear end. By filling the ink follower, effects such as improved ink followability, remaining amount visibility and prevention of solvent volatilization can be expected. The ink follower is preferably composed of a component that is incompatible with the ink composition. When an alcohol solvent or a glycol ether solvent is used as the ink solvent, for example, a highly viscous silicone oil, a hydrocarbon oil, etc. Can be used.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples. The part of the amount used in the following examples is part by mass.

Preparation of Ink Composition Regarding the ink composition, when the colorant is a pigment, it is dissolved in a bead mill, three rolls, etc. together with a solvent and a resin, and then the polyurethane resin (A2) solution of the example and the comparative example BYK-410 was added and stirred further to obtain the final ink composition.
Table I below shows the components of each ink composition (Example, Comparative Example).

  The ink obtained as described above was filled, and the following evaluation test was performed. The ballpoint pen used in the test has a polypropylene tube having an inner diameter of 1.60 mm and a stainless tip (the ball is a cemented carbide and has a diameter of 1.0 mm).

Evaluation Method Viscosity: Measured using an E-type rotational viscometer at 25 ° C. and shear rates: 3.83 / s ⁻¹ and 38.3 / s ⁻¹ .
Stickiness: After filling the obtained ink into a ballpoint pen, the amount of ink attached to the chip holder was observed after writing with a mechanical writing tester under conditions of a speed of 4.5 m / min, an angle of 60 °, and a load of 200 g. . Evaluation was made with “O” indicating that there was almost no ink void and “X” indicating that there was a lot of ink.

  DC property: The obtained ink was filled in a ballpoint pen, and then the pen body was left facing downward in a thermostat at 50 ° C. and 80% for 24 hours, and the ink direct current phenomenon from the pen tip was observed. Evaluations were made with “○” indicating that there was almost no direct current phenomenon, and “×” indicating many.

  The evaluation results are listed together with the ink compositions of Table I. Examples 1 to 5 are invention examples. In these examples, polyurethane resin (A2) was added and the solvent was changed. The obtained ink showed a good thixotropic property, and showed good results with respect to the stickiness and direct current. Comparative Example 1 in which the polyurethane resin (A2) was not added did not show sufficient thixotropic properties, and a direct current phenomenon was observed.

Claims (7)

An oil ballpoint pen ink composition comprising at least a colorant and an organic solvent, wherein the ink composition further comprises a polyurethane resin (A) represented by the following general formula:

(In the above formula, n is 3 to 15, R ₁ and R ₂ are each an aliphatic hydrocarbon having 2 to 6 carbon atoms)
An ink composition for oil-based ballpoint pens comprising: 2. The oil-based ballpoint pen according to claim 1, wherein the ratio of the viscosity at a shear rate of 3.8 sec ^{−1 to} the viscosity at 25 ° C. and a shear rate of 38 sec ⁻¹ of the ink composition is 1.2 to 4. Ink composition. The ink composition for oil-based ballpoint pens according to claim 1 or 2, wherein the viscosity of the ink composition at 25 ° C and a shear rate of 380 sec ^-1 is 100 mPa · s to 1000 mPa · s.   The ink composition for oil-based ballpoint pens according to any one of claims 1 to 3, wherein the addition amount of the polyurethane resin (A) is 0.1 to 5% by mass with respect to the total mass of the ink composition. object. The ink composition for a pressurized oil ballpoint pen according to claim 1 or 2, wherein the ink composition has a viscosity of 100 to 5000 mPa · s at 25 ° C and a shear rate of 380 sec- ¹ .   6. The pressurized oil ballpoint pen according to claim 1, wherein the addition amount of the polyurethane resin (A) is 0.1 to 10% by mass relative to the total mass of the ink composition. Ink composition.   The ball-point pen carrying the ink composition for oil-based ball-point pens as described in any one of Claims 1-6.